NEW YORK — Mets right-hander Shaun Marcum is scheduled to arrive in New York Thursday to be examined by team doctors, and his scheduled start Sunday against the Marlins will likely be made by lefty Aaron Laffey.

Marcum, whom the Mets are hoping will help solidify their starting rotation, was slated to pitch a simulated game Tuesday but experienced neck pain while warming up and was shut down.

The exact nature of his injury has been shrouded in mystery with the diagnosis first being a right shoulder impingement and later a right biceps strain. The veteran has a history of right elbow and shoulder problems.

"He’ll be here Thursday to see our doctors to get a better idea of what the issues are," manager Terry Collins said before last night’s game against the Padres at Citi Field.

"The way I’m hearing it — obviously we have to wait until the doctors tell us — he has a little discomfort running from his (right) shoulder up to his neck. What that is, where it starts, what is causing it, I think we won’t know until he sees the doctor."

Laffey, 27, has made several major-league stops.

In six seasons, he has played with Cleveland, Seattle, the Yankees and Toronto, posting a 25-29 career record with a 4.38 ERA in 148 games, 65 starts.

Last season, he posted a 4-6 mark with a 4.56 ERA in 22 games, 16 starts, with the Blue Jays.

Laffey, who was signed by the Mets as a free agent in December, isn’t on the 40-man roster. To make room for him, the Mets are expected to move Johan Santana from the 15-day DL to the 60-day DL to vacate a spot on the 40-man roster.

In a pre-emptive move, the Mets began stretching out Laffey in late March as insurance in the wake of Santana’s injury. Collins has set his pitch count between 90 and 95.

"There’s a couple of other options we have, (but) we just thought in spring training from what we saw from Aaron Laffey, that, due to his experience — he’s had some success at this level — that he would be our first option right now," said Collins. He added that he also considered veterans Collin McHugh and Chris Schwinden, both of whom pitched with the Mets last season.

"Hopefully, he comes in Sunday and pitches very well," Collins said. "If he does, he most likely will get another start."

Marcum, who was originally slated to start last night against San Diego, initially felt pain during a bullpen session last Monday.

He received a cortisone shot the next day. His latest setback comes two days after the Mets placed him on the 15-day disabled list retroactive to March 22.

Signed to a one-year, $4 million deal plus incentives as a free agent this offseason, he posted a 4.66 ERA over 9⅔ innings in three starts in spring training.

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With a biting wind and temperatures expected to dip into 20s with the wind-chill factor, Collins said he's keeping a close eye on starter Matt Harvey tonight.

"My biggest worry is the time between innings," Collins said. "If he's out there and he pitched four innings and we have a 20-minute half inning, then it becomes an issue. I know our dugouts are heated. We do have a place for him to stay warm.

"But when this baby begins to drop down in the 20s wind-chill factor-wise, it becomes an issue."